Alternating current rectifying circuit and alternating current rectifying method for driving led module

ABSTRACT

Disclosed are an alternating current rectifying circuit and an alternating current rectifying method for driving an LED module. By using the present invention, stability of an output voltage can be improved, and luminous efficiency of the LED module can be improved.

This application is a continuation of U.S. patent application Ser. No.14/762,709, filed on Jul. 22, 2015, which claims priority to PCTApplication No. PCT/CN2013/090328, filed on Dec. 24, 2013, and ChinesePatent Application No. 201310037178.9, filed China State IntellectualProperty Office on Jan. 31, 2013, titled “Alternating current rectifyingcircuit and alternating current rectifying method for driving LEDmodule”, the entire contents of which are incorporated herein byreference.

TECHNICAL FIELD

The present disclosure relates to the technique of alternating currentrectification, and more particularly, to an alternating currentrectifying circuit and an alternating current rectifying method fordriving an LED (Light Emitting Diode) module.

BACKGROUND

As one kind of new light sources with high-efficiency, LED (LightEmitting Diode) modules are widely applied in illumination incommercial, industrial and domestic fields due to advantages such as along lifespan, a low energy consumption, energy-saving and environmentalprotection.

When the LED module acts as a light source of an illumination device,the lifespan of the illumination device not only depends on anillumination performance of the LED, but also depends on stability ofdriving circuit components for providing a working voltage for the LEDmodule. In conventional application solutions, the bottleneck of thelifespan of the LED module still lies in the stability of the voltageprovided by the driving circuit. In order to reduce the influence offluctuation of the driving voltage to the lifespan of the LED module, itis necessary to design a new alternating current rectifying circuit forproviding a stable driving voltage to drive the LED module based on thewidely applied alternating current at present.

In a bridge rectifier circuit, semiconductor rectifier diodes (or nameddiodes) are connected to form a simple rectifying circuit. The bridgerectifier circuit is widely applied in various voltage-stabilizingapplications for AC-DC conversion. Through the bridge rectifier circuit,the alternating current (AC) is rectified into the direct current (DC),so as to provide a relatively stable voltage for the LED module and thuslengthen the service life of the LED module.

FIG. 1 is a schematic diagram illustrating a structure of a conventionalalternating current rectifying circuit for driving an LED module. TheLED module is connected to a DC output terminal of the alternatingcurrent rectifying circuit. The alternating current is rectified by thealternating current rectifying circuit so as to be capable of directlydriving the LED module. Referring to FIG. 1, the alternating currentrectifying circuit is a bridge rectifier circuit, and includes analternating current module (AC), a first diode D1, a second diode D2, athird diode D3 and a fourth diode D4.

A positive terminal of the first diode D1 is connected with a negativeterminal of the second diode D2, and a negative terminal of the firstdiode D1 is connected with a negative terminal of the third diode D3 andan input terminal (V+) of an external LED module.

A positive terminal of the second diode D2 is connected with a positiveterminal of the fourth diode D4 and an output terminal (V−) of theexternal LED module.

A positive terminal of the third diode D3 is connected with a negativeterminal of the fourth diode D4.

One end (A1) of the alternating current module is connected with thepositive terminal of the first diode D1, and the other end (A2) thereofis connected with the positive terminal of the third diode D3.

A cycle of the alternating current includes a positive half cycle and anegative half cycle, wherein the positive half cycle is a time periodduring which the alternating current ascends to a positive peak valuefrom a zero value and descends from the positive peak value to the zerovalue; and the negative half cycle is a time period during which thealternating current descends to a negative peak value from the zerovalue and ascends from the negative peak value to the zero value.

During the positive half cycle of the alternating current, thealternating current outputted from the alternating module passes throughthe first diode D1, the external LED module and the fourth diode D4 soas to form a current loop for providing working voltage for the externalLED module.

During the negative half cycle of the alternating current, thealternating current outputted from the alternating module passes throughthe third diode D3, the external LED module and the second diode D2 soas to form another current loop for providing working voltage for theexternal LED module.

From above, in the conventional alternating current rectifying circuitfor driving the LED module, the alternating current, after beingrectified by the diodes, directly drives the LED module to operate. Thealternating current fluctuates periodically, and the LED module has acertain switching-on voltage, i.e., only when the voltage applied acrossthe LED module exceeds the switching-on voltage, the LED module may beturned on and may emit light; and if the voltage applied across the LEDmodule does not exceed the switching-on voltage, the LED module is in acut-off status, i.e., in a status of not emitting light. Thereby, thevoltage which can be provided by the conventional alternating currentrectifying circuit to the external LED module when the current loopreverses its current direction is smaller than the switching-on voltage,thus the luminous efficiency of the LED module is relatively low;further, through the rectification by the diodes in the alternatingcurrent rectifying circuit, the voltage value outputted to the LEDmodule fluctuates as the fluctuation of the alternating voltage, therebythe stability of the output voltage is relatively low, and obviousflickering phenomenon appears in the LED module, which shortens theservice life of the LED module.

SUMMARY

The embodiments of the present disclosure provide an alternating currentrectifying circuit for driving an LED module, which improves stabilityof an output voltage and improves luminous efficiency of the LED module.

The embodiments of the present disclosure also provide an alternatingcurrent rectifying method for driving an LED module, which improvesstability of an output voltage and improves luminous efficiency of theLED module.

In order to achieve the above purposes, the embodiments of the presentdisclosure provide an alternating current rectifying circuit for drivingan LED module, the alternating current rectifying circuit including: analternating current module, a positive half cycle rectifying branch, apositive half cycle feeding branch, a negative half cycle rectifyingbranch, a negative half cycle feeding branch, and an overvoltageprotection branch, wherein:

the positive half cycle rectifying branch is configured to, when thealternating current module is in a positive half cycle, rectify analternating current outputted from the alternating current module, andoutput the rectified voltage signal to the overvoltage protection branchand an external LED module;

the positive half cycle feeding branch is configured to perform chargingaccording to the alternating current outputted from the alternatingcurrent module when the alternating current module is in a negative halfcycle; and perform discharging and output the discharged voltage signalto the overvoltage protection branch and the external LED module whenthe alternating current module is in the positive half cycle;

the negative half cycle rectifying branch is configured to, when thealternating current module is in the negative half cycle, rectify thealternating current outputted from the alternating current module, andoutput the rectified voltage signal to the overvoltage protection branchand the external LED module;

the negative half cycle feeding branch is configured to perform chargingaccording to the alternating current outputted from the alternatingcurrent module when the alternating current module is in the positivehalf cycle; and perform discharging and output the discharged voltagesignal to the overvoltage protection branch and the external LED modulewhen the alternating current module is in the negative half cycle; and

the overvoltage protection branch is configured to turn off anelectrical path of the external LED module when the inputted voltagesignal is higher than a preset voltage threshold.

Preferably, the positive half cycle rectifying branch includes a firstrectifying tube, a second rectifying tube and a sixth rectifying tube,wherein:

a positive terminal of the second rectifying tube is connected with oneend of the alternating current module, and a negative terminal of thesecond rectifying tube is connected with a positive terminal of thefirst rectifying tube;

a negative terminal of the first rectifying tube is connected with aninput terminal of the external LED module;

a positive terminal of the sixth rectifying tube is connected with anoutput terminal of the external LED module, and a negative terminal ofthe sixth rectifying tube is connected with the other end of thealternating current module.

Preferably, the negative half cycle rectifying branch includes a thirdrectifying tube, a fourth rectifying tube and a fifth rectifying tube,wherein:

a negative terminal of the third rectifying tube is connected with theone end of the alternating current module, and a positive terminal ofthe third rectifying tube is connected with the output terminal of theexternal LED module;

a positive terminal of the fifth rectifying tube is connected with theother end of the alternating current module, and a negative terminal ofthe fifth rectifying tube is connected with a positive terminal of thefourth rectifying tube; and

a negative terminal of the fourth rectifying tube is connected with theinput terminal of the external LED module.

Preferably, the positive half cycle feeding branch includes a firstcapacitor and a fourth capacitor, wherein:

one end of the first capacitor is connected with the positive terminalof the fourth rectifying tube, and the other end of the first capacitoris connected with the one end of the alternating current module; and

one end of the fourth capacitor is connected with the other end of thealternating current module, and the other end of the fourth capacitor isconnected with the output terminal of the external LED module.

Preferably, the negative half cycle feeding branch includes a secondcapacitor and a third capacitor, wherein:

one end of the second capacitor is connected with the one end of thealternating current module, and the other end of the second capacitor isconnected with the output terminal of the external LED module; and

one end of the third capacitor is connected with the positive terminalof the first rectifying tube, and the other end of the third capacitoris connected with the other end of the alternating current module.

Preferably, the overvoltage protection branch includes a first resistor,a second resistor, a third resistor, a fourth resistor, a fifthresistor, a first Zener diode, a second Zener diode, a NPN transistorand a field effect transistor, wherein:

one end of the first resistor is connected with one end of the fourthresistor and the input terminal of the LED module, and the other end ofthe first resistor is connected with one end of the second resistor, anegative terminal of the first Zener diode and one end of the thirdresistor;

the other end of the third resistor is connected with a base of the NPNtransistor;

the other end of the fourth resistor is connected with a collector ofthe NPN transistor, one end of the fifth resistor and a negativeterminal of the second Zener diode;

the other end of the fifth resistor is connected with a gate of thefield effect transistor;

a drain of the field effect transistor is connected with the outputterminal of the LED module; and

a source of the field effect transistor is connected with the other endof the second resistor, a positive terminal of the first Zener diode, anemitter of the NPN transistor, a positive terminal of the second Zenerdiode and a positive terminal of the third rectifying tube.

Preferably, the rectifying tubes are diodes, transistors or siliconcontrolled rectifiers.

Preferably, the first capacitor, the second capacitor, the thirdcapacitor and the fourth capacitor are non-polar capacitors.

Preferably, the first capacitor, the second capacitor, the thirdcapacitor and the fourth capacitor have the same capacitance value.

Preferably, during the positive half cycle of the alternating current,the current passes through the second rectifying tube, the firstrectifying tube, the LED module and the sixth rectifying tube to form aloop so as to supply power to the LED module, and output the rectifiedvoltage signal to the overvoltage protection branch, and the overvoltageprotection branch determines whether to turn off the electrical path ofthe LED module according to the inputted voltage signal and the presetvoltage threshold, wherein:

during an ascending stage of voltage of the alternating current, thealternating current passes through the second rectifying tube and thethird capacitor to form a loop so as to charge the third capacitor;meanwhile, the alternating current passes through the second capacitorand the sixth rectifying tube to form a loop so as to charge the secondcapacitor; meanwhile, the fourth capacitor, the first capacitor, thefourth rectifying tube and the LED module form a loop so as to supplypower to the LED module;

during the negative half cycle of the alternating current, the currentpasses through the fifth diode, the fourth rectifying tube, the LEDmodule and the third rectifying tube to form a loop so as to supplypower to the LED module, and output the rectified voltage signal to theovervoltage protection branch, and the overvoltage protection branchdetermines whether to turn off the electrical path of the LED moduleaccording to the inputted voltage signal and the preset voltagethreshold, wherein:

during an ascending stage of an absolute value of voltage, thealternating current in the alternating current module passes through thefifth rectifying tube and the first capacitor to form a loop so as tocharge the first capacitor; meanwhile, the alternating current passesthrough the fourth capacitor and the third rectifying tube to form aloop so as to charge the fourth capacitor; meanwhile, the secondcapacitor, the third capacitor, the first rectifying tube and the LEDmodule form a loop so as to supply power to the LED module.

Preferably, the alternating current rectifying circuit further includes:a current regulative diode with a positive terminal connected with thesource of the field effect transistor and a negative terminal connectedwith the positive terminal of the third rectifying tube.

Preferably, the alternating current rectifying circuit further includes:an electrolytic capacitor with a positive terminal connected with theinput terminal of the LED module and a negative terminal connected withthe output terminal of the LED module.

An alternating current rectifying method for driving a light emittingdiode LED module is provided, wherein the LED module is driven by analternating current rectifying circuit and the alternating currentrectifying circuit includes: an alternating current module, a positivehalf cycle rectifying branch, a positive half cycle feeding branch, anegative half cycle rectifying branch, a negative half cycle feedingbranch, and an overvoltage protection branch, the method including:

when the alternating current module is in a positive half cycle, thepositive half cycle rectifying branch rectifies an alternating currentoutputted from the alternating current module, and outputs the rectifiedvoltage signal to the overvoltage protection branch and an external LEDmodule;

the negative half cycle feeding branch performs charging according tothe alternating current outputted from the alternating current module,and the positive half cycle feeding branch performs discharging andoutputs the discharged voltage signal to the overvoltage protectionbranch and the external LED module;

the overvoltage protection branch turns off an electrical path of theexternal LED module when the inputted voltage signal is higher than apreset voltage threshold;

when the alternating current module is in the negative half cycle, thenegative half cycle rectifying branch rectifies the alternating currentoutputted from the alternating current module, and outputs the rectifiedvoltage signal to the overvoltage protection branch circuit and theexternal LED module;

the negative half cycle feeding branch performs discharging, and outputsthe discharged voltage signal to the overvoltage protection branch andthe external LED module, and the positive half cycle feeding branchperforms charging according to the alternating current outputted fromthe alternating current module; and

the overvoltage protection branch turns off the electrical path of theexternal LED module when the inputted voltage signal is higher than thepreset voltage threshold.

The positive half cycle rectifying branch includes a first rectifyingtube, a second rectifying tube and a sixth rectifying tube, wherein:

a positive terminal of the second rectifying tube is connected with oneend of the alternating current module, and a negative terminal of thesecond rectifying tube is connected with a positive terminal of thefirst rectifying tube;

a negative terminal of the first rectifying tube is connected with aninput terminal of the external LED module; and

a positive terminal of the sixth rectifying tube is connected with anoutput terminal of the external LED module, and a negative terminal ofthe sixth rectifying tube is connected with the other end of thealternating current module.

The negative half cycle rectifying branch includes a third rectifyingtube, a fourth rectifying tube and a fifth rectifying tube, wherein:

a negative terminal of the third rectifying tube is connected with theone end of the alternating current module, and a positive terminal ofthe third rectifying tube is connected with the output terminal of theexternal LED module;

a positive terminal of the fifth rectifying tube is connected with theother end of the alternating current module, and a negative terminal ofthe fifth rectifying tube is connected with a positive terminal of thefourth rectifying tube; and

a negative terminal of the fourth rectifying tube is connected with theinput terminal of the external LED module.

The positive half cycle feeding branch includes a first capacitor and afourth capacitor, wherein:

one end of the first capacitor is connected with the positive terminalof the fourth rectifying tube, and the other end of the first capacitoris connected with the one end of the alternating current module; and

one end of the fourth capacitor is connected with the other end of thealternating current module, and the other end of the fourth capacitor isconnected with the output terminal of the external LED module.

The negative half cycle feeding branch includes a second capacitor and athird capacitor, wherein:

one end of the second capacitor is connected with the one end of thealternating current module, and the other end of the second capacitor isconnected with the output terminal of the external LED module; and

one end of the third capacitor is connected with the positive terminalof the first rectifying tube, and the other end of the third capacitoris connected with the other end of the alternating current module.

The overvoltage protection branch includes a first resistor, a secondresistor, a third resistor, a fourth resistor, a fifth resistor, a firstZener diode, a second Zener diode, a NPN transistor and a field effecttransistor, wherein:

one end of the first resistor is connected with one end of the fourthresistor and the input terminal of the LED module, and the other end ofthe first resistor is connected with one end of the second resistor, anegative terminal of the first Zener diode and one end of the thirdresistor;

the other end of the third resistor is connected with a base of the NPNtransistor;

the other end of the fourth resistor is connected with a collector ofthe NPN transistor, one end of the fifth resistor and a negativeterminal of the second Zener diode;

the other end of the fifth resistor is connected with a gate of thefield effect transistor;

a drain of the field effect transistor is connected with the outputterminal of the LED module; and

a source of the field effect transistor is connected with the other endof the second resistor, a positive terminal of the first Zener diode, anemitter of the NPN transistor, a positive terminal of the second Zenerdiode and a positive terminal of the third rectifying tube.

The rectifying tubes are diodes, during the positive half cycle of thealternating current, the current passes through the second diode, thefirst diode, the LED module and the sixth diode to form a loop so as tosupply power to the LED module, and output the rectified voltage signalto the overvoltage protection branch, and the overvoltage protectionbranch determines whether to turn off the electrical path of the LEDmodule according to the inputted voltage signal and the preset voltagethreshold, wherein:

during an ascending stage of voltage of the alternating current, thealternating current passes through the second diode and the thirdcapacitor to form a loop so as to charge the third capacitor; meanwhile,the alternating current passes through the second capacitor and thesixth diode to form a loop so as to charge the second capacitor;meanwhile, the fourth capacitor, the first capacitor, the fourth diodeand the LED module form a loop so as to supply power to the LED module;

during the negative half cycle of the alternating current, the currentpasses through the fifth diode, the fourth diode, the LED module and thethird diode to form a loop so as to supply power to the LED module, andoutput the rectified voltage signal to the overvoltage protectionbranch, and the overvoltage protection branch determines whether to turnoff the electrical path of the LED module according to the inputtedvoltage signal and the preset voltage threshold, wherein:

during an ascending stage of an absolute value of voltage, thealternating current in the alternating current module passes through thefifth diode and the first capacitor to form a loop so as to charge thefirst capacitor; meanwhile, the alternating current passes through thefourth capacitor and the third diode to form a loop so as to charge thefourth capacitor; meanwhile, the second capacitor, the third capacitor,the first diode and the LED module form a loop so as to supply power tothe LED module.

It can be seen from the above technical solutions, the alternatingcurrent rectifying circuit and the alternating current rectifying methodfor driving a light emitting diode LED module provided by theembodiments of the present disclosure include: an alternating currentmodule, a positive half cycle rectifying branch, a positive half cyclefeeding branch, a negative half cycle rectifying branch, a negative halfcycle feeding branch, and an overvoltage protection branch, wherein: thepositive half cycle rectifying branch is configured to rectify analternating current outputted from the alternating current module andoutput the rectified voltage signal to the overvoltage protection branchand an external LED module when the alternating current module is in apositive half cycle; the positive half cycle feeding branch isconfigured to perform charging according to the alternating currentoutputted from the alternating current module when the alternatingcurrent module is in a negative half cycle; and perform discharging andoutput the discharged voltage signal to the overvoltage protectionbranch and the external LED module when the alternating current moduleis in the positive half cycle; the negative half cycle rectifying branchis configured to rectify the alternating current outputted from thealternating current module and output the rectified voltage signal tothe overvoltage protection branch and the external LED module when thealternating current module is in the negative half cycle; the negativehalf cycle feeding branch is configured to perform charging according tothe alternating current outputted from the alternating current modulewhen the alternating current module is in the positive half cycle; andperform discharging and output the discharged voltage signal to theovervoltage protection branch and the external LED module when thealternating current module is in the negative half cycle; and theovervoltage protection branch is configured to turn off an electricalpath of the external LED module when the inputted voltage signal ishigher than a preset voltage threshold. In this way, on the basis of theconventional circuit in which the alternating current directly drivesthe LED module, by utilizing the charging and discharging of thecapacitors, the stability of the output voltage is improved, theutilization rate of each half cycle of the alternating current isimproved, the conduction time of the LED is increased, the fluctuationof light emitted by the LED is reduced, the relatively high power factoris ensured, and the luminous efficiency of the LED module is improved.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to explain the technical solutions in the embodiments of thepresent disclosure or in the prior art more clearly, the drawingsnecessary for describing the embodiments or the prior art will be simplyintroduced below. Apparently, the drawings in the following descriptiononly illustrate some embodiments of the present disclosure, for theperson skilled in the art, other embodiments and drawings may also beobtained according to the embodiments shown in these drawings.

FIG. 1 is a schematic diagram illustrating a structure of a conventionalalternating current rectifying circuit for driving an LED module.

FIG. 2 is a schematic diagram illustrating a structure of an alternatingcurrent rectifying circuit for driving an LED module according to anembodiment of the present disclosure.

FIG. 3 is a schematic diagram illustrating a detailed structure of analternating current rectifying circuit for driving an LED moduleaccording to an embodiment of the present disclosure.

FIG. 4 is a schematic diagram illustrating another detailed structure ofan alternating current rectifying circuit for driving an LED moduleaccording to an embodiment of the present disclosure.

FIG. 5 is a schematic diagram illustrating further another detailedstructure of an alternating current rectifying circuit for driving anLED module according to an embodiment of the present disclosure.

FIG. 6 is a flow chart of an alternating current rectifying method fordriving an LED module according to an embodiment of the presentdisclosure.

DETAILED DESCRIPTION

Hereinafter, the technical solutions of respective embodiments in thepresent disclosure will be described clearly and completely incombination with the accompanying drawings. Apparently, the describedembodiments are only part of the embodiments of the present disclosure,rather than all of the embodiments. Based on the embodiments in thepreset disclosure, all the other embodiments which could be obtained bythe person skilled in the art without paying inventive labor belong tothe scope protected by the present disclosure.

In the conventional alternating current rectifying circuit for drivingthe LED module, since the alternating current fluctuates periodically,and the LED module has a certain switching-on voltage, the voltage whichcan be provided to the external LED module when the current loop turnsits direction is smaller than the switching-on voltage, thus theluminous efficiency of the LED module is relatively low; further,through the rectification by the diodes in the alternating currentrectifying circuit, the voltage value outputted to the LED modulefluctuates as the fluctuation of the alternating voltage, thereby thestability of the output voltage is relatively low, which influences theservice life of the LED module.

With respect to the deficiencies in the prior art in which thealternating current directly drives the circuit, the embodiments of thepresent disclosure provide a driving circuit for directly driving theLED module by using an alternating current which provides a drivingcurrent for the LED module, i.e., charging and discharging of capacitorsare used to increase a conduction angle and fill a trough of thealternating current, so as to improve efficiency of power supply andreduce flickering phenomenon in the LED.

FIG. 2 is a schematic diagram illustrating a structure of an alternatingcurrent rectifying circuit for driving an LED module according to anembodiment of the present disclosure. Referring to FIG. 2, thealternating current rectifying circuit includes: an alternating currentmodule, a positive half cycle rectifying branch, a positive half cyclefeeding branch, a negative half cycle rectifying branch, a negative halfcycle feeding branch, and an overvoltage protection branch, wherein:

the positive half cycle rectifying branch rectifies an alternatingcurrent outputted from the alternating current module and outputs therectified voltage signal to the overvoltage protection branch and anexternal LED module when the alternating current module is in a positivehalf cycle;

the positive half cycle feeding branch performs charging according tothe alternating current outputted from the alternating current modulewhen the alternating current module is in a negative half cycle; andperforms discharging and outputs the discharged voltage signal to theovervoltage protection branch and the external LED module when thealternating current module is in the positive half cycle;

the negative half cycle rectifying branch rectifies the alternatingcurrent outputted from the alternating current module and outputs therectified voltage signal to the overvoltage protection branch and theexternal LED module when the alternating current module is in thenegative half cycle;

the negative half cycle feeding branch performs charging according tothe alternating current outputted from the alternating current modulewhen the alternating current module is in the positive half cycle; andperforms discharging and outputs the discharged voltage signal to theovervoltage protection branch and the external LED module when thealternating current module is in the negative half cycle; and

the overvoltage protection branch turns off an electrical path of theexternal LED module when the inputted voltage signal is higher than apreset voltage threshold.

In the embodiments of the present disclosure, the external LED modulemay also be other load modules, such as other loads which need to be ina stable working voltage.

The positive half cycle rectifying branch includes a first rectifyingtube D1, a second rectifying tube D2 and a sixth rectifying tube D6 (notshown in the drawing), wherein:

a positive terminal of the second rectifying tube D2 is connected withone end (A1) of the alternating current module, and a negative terminalof the second rectifying tube D2 is connected with a positive terminalof the first rectifying tube D1;

a negative terminal of the first rectifying tube D1 is connected with aninput terminal of the external LED module;

a positive terminal of the sixth rectifying tube D6 is connected with anoutput terminal of the external LED module, and a negative terminal ofthe sixth rectifying tube D6 is connected with the other end (A2) of thealternating current module.

The negative half cycle rectifying branch includes a third rectifyingtube D3, a fourth rectifying tube D4 and a fifth rectifying tube D5 (notshown in the drawing), wherein:

a negative terminal of the third rectifying tube D3 is connected withthe one end (A1) of the alternating current module, and a positiveterminal of the third rectifying tube D3 is connected with the outputterminal of the external LED module;

a positive terminal of the fifth rectifying tube D5 is connected withthe other end (A2) of the alternating current module, and a negativeterminal of the fifth rectifying tube D5 is connected with a positiveterminal of the fourth rectifying tube D4;

a negative terminal of the fourth rectifying tube D4 is connected withthe input terminal of the external LED module.

The positive half cycle feeding branch includes a first capacitor C1 anda fourth capacitor C4 (not shown in the drawing), wherein:

one end of the first capacitor C1 is connected with the positiveterminal of the fourth rectifying tube D4, and the other end of thefirst capacitor C1 is connected with the one end (A1) of the alternatingcurrent module;

one end of the fourth capacitor C4 is connected with the other end (A2)of the alternating current module, and the other end of the fourthcapacitor C4 is connected with the output terminal of the external LEDmodule.

The negative half cycle feeding branch includes a second capacitor C2and a third capacitor C3 (not shown in the drawing), wherein:

one end of the second capacitor C2 is connected with the one end (A1) ofthe alternating current module, and the other end of the secondcapacitor C2 is connected with the output terminal of the external LEDmodule;

one end of the third capacitor C3 is connected with the positiveterminal of the first rectifying tube D1, and the other end of the thirdcapacitor C3 is connected with the other end (A2) of the alternatingcurrent module.

The overvoltage protection branch includes a first resistor R1, a secondresistor R2, a third resistor R3, a fourth resistor R4, a fifth resistorR5, a first Zener diode DZ1, a second Zener diode DZ2, a NPN transistorQ1 and a field effect transistor M1 (not shown in the drawing), wherein:

one end of the first resistor R1 is connected with one end of the fourthresistor R4 and the input terminal of the LED module, and the other endof the first resistor R1 is connected with one end of the secondresistor R2, a negative terminal of the first Zener diode DZ1 and oneend of the third resistor R3;

the other end of the third resistor R3 is connected with a base of theNPN transistor Q1;

the other end of the fourth resistor R4 is connected with a collector ofthe NPN transistor Q1, one end of the fifth resistor R5 and a negativeterminal of the second Zener diode DZ2;

the other end of the fifth resistor R5 is connected with a gate of thefield effect transistor M1;

a drain of the field effect transistor M1 is connected with the outputterminal of the LED module;

a source of the field effect transistor M1 is connected with the otherend of the second resistor R2, a positive terminal of the first Zenerdiode DZ1, an emitter of the NPN transistor Q1, a positive terminal ofthe second Zener diode DZ1 and a positive terminal of the thirdrectifying tube D3.

In the embodiments of the present disclosure, the first resistor R1, thesecond resistor R2, the third resistor R3, the fourth resistor R4, thefifth resistor R5, the first Zener diode DZ1, the second Zener diodeDZ2, the NPN transistor Q1 and the field effect transistor M1 constitutethe overvoltage protection circuit. When the inputted voltage is higherthan the preset voltage threshold, the electronic path of the externalLED module is turned off, i.e., the field effect transistor M1 is turnedoff, and the current is cut off, so as to effectively protect the LEDmodule and the entire circuit from being damaged and greatly improve thereliability of the circuit.

In actual applications, the voltage threshold may be set according toactual requirements. By setting the resistances of the first resistor R1and the second resistor R2, the voltage threshold may be determined bythe voltage divided by the first resistor R1 and the second resistor R2.

Preferably, the rectifying tubes may diodes, or may be transistors, ormay be any devices having a unidirectional conductive characteristic,such as silicon controlled rectifiers. The semiconductor rectifier diodeis preferably adopted, since the semiconductor rectifier diode has a lowcost, and is convenient to be secondarily integrated with the LED moduleto constitute an integrated LED illumination device directly driven bythe alternating current.

For example, the diode is used as the rectifying tube. In this case, thedetailed explanation of the embodiments of the present disclosure willbe given below.

FIG. 3 is a schematic diagram illustrating a detailed structure of analternating current rectifying circuit for driving an LED moduleaccording to an embodiment of the present disclosure. Referring to FIG.3, the alternating current rectifying circuit for driving an LED moduleincludes: a first diode D1, a second diode D2, a third diode D3, afourth diode D4, a fifth diode D5, a sixth diode D6, a first capacitorC1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4,an LED module, a first resistor R1, a second resistor R2, a thirdresistor R3, a fourth resistor R4, a fifth resistor R5, a first Zenerdiode DZ1, a second Zener diode DZ2, a NPN transistor Q1 and a fieldeffect transistor M1, wherein:

a positive terminal of the second diode D2 is connected with one end(A1) of the alternating current module, and a negative terminal of thesecond diode D2 is connected with a positive terminal of the first diodeD1 and one end of the third capacitor C3;

a negative terminal of the first diode D1 is connected with a negativeterminal of the fourth diode D4 and an input terminal (V+) of anexternal LED module;

the other end of the third capacitor C3 is connected with the other end(A2) of the alternating current module.

a positive terminal of the fourth diode D4 is connected with a negativeterminal of the fifth diode D5 and one end of the first capacitor C1;

the other end of the first capacitor C1 is connected with the one end(A1) of the alternating current module;

a positive terminal of the fifth diode tube D5 is connected with anegative terminal of the sixth diode D6, one end of the fourth capacitorC4 and the other end (A2) of the alternating current module;

a negative terminal of the third diode D3 is connected with the one endof the second capacitor C2 and the one end (A1) of the alternatingcurrent module;

an output terminal (V−) of the LED module is connected with a positiveterminal of the third diode D3, the other end of the second capacitorC2, the other end of the fourth capacitor C4, and a positive terminal ofthe sixth diode D6;

one end of the first resistor R1 is connected with one end of the fourthresistor R4 and the input terminal of the LED module, the other end ofthe first resistor R1 is connected with one end of the second resistorR2, a negative terminal of the first Zener diode DZ1 and one end of thethird resistor R3;

the other end of the third resistor R3 is connected with a base of theNPN transistor Q1;

the other end of the fourth resistor R4 is connected with a collector ofthe NPN transistor Q1, one end of the fifth resistor R5 and a negativeterminal of the second Zener diode DZ2;

the other end of the fifth resistor R5 is connected with a gate of thefield effect transistor M1;

a drain of the field effect transistor M1 is connected with the outputterminal of the LED module;

a source of the field effect transistor M1 is connected with the otherend of the second resistor R2, a positive terminal of the first Zenerdiode DZ1, an emitter of the NPN transistor Q1, a positive terminal ofthe second Zener diode DZ2 and a positive terminal of the third diodeD3.

In the embodiments of the present disclosure, the first capacitor C1,the second capacitor C2, the third capacitor C3 and the fourth capacitorC4 operate in an alternating state, and need to endure an inversevoltage. Preferably, the first capacitor C1, the second capacitor C2,the third capacitor C3 and the fourth capacitor C4 are non-polarcapacitors, so as to be adaptable to the alternating workingcircumstance. The alternating withstanding voltage value of thenon-polar capacitor should be greater than or at least equal to thealternating input voltage value.

Preferably, the first capacitor C1, the second capacitor C2, the thirdcapacitor C3 and the fourth capacitor C4 have the same or similarcapacitance value.

Hereinafter, the operational principle of the circuit in the embodimentsof the present disclosure will be described:

during the positive half cycle of the alternating current, currentpasses through the second diode D2, the first diode D1, the LED moduleand the sixth diode D6 to form a loop so as to supply power to the LEDmodule, and output the rectified voltage signal to the overvoltageprotection branch, and the overvoltage protection branch determineswhether to turn off the electrical path of the LED module according tothe inputted voltage signal and the preset voltage threshold, wherein:

during an ascending stage of the alternating current voltage, thealternating current passes through the second diode D2 and the thirdcapacitor C3 to form a loop so as to charge the third capacitor C3;meanwhile, the alternating current passes through the second capacitorC2 and the sixth diode D6 to form a loop so as to charge the secondcapacitor C2; meanwhile, the fourth capacitor C4, the first capacitorC1, the fourth diode D4 and the LED module form a loop so as to supplypower to the LED module, i.e., electric charges stored in the firstcapacitor C1 and the fourth capacitor C4 are discharged to the LEDmodule through the fourth diode D4, so as to provide the working voltagefor the LED module.

In the embodiments of the present disclosure, during the ascending stageof the alternating current voltage, in the circuit structure, the secondcapacitor C2 and the third capacitor C3 are connected in parallel, thefirst capacitor C1 and the fourth capacitor C4 are connected with thealternating current module in series so as to supply power to the LEDmodule, such that the voltage of the alternating current is increasedwhen the alternating current module initially supplies power or switchesthe positive and negative half cycles, so as to enable the LED module tobe turned on in advance, in this way, the quality factor of the circuitis improved, the stability of the output voltage is improved, theluminous efficiency of the LED module is improved, and the service lifeof the LED module is prolonged.

During the negative half cycle of the alternating current, currentpasses through the fifth diode D5, the fourth diode D4, the LED moduleand the third diode D3 to form a loop so as to supply power to the LEDmodule, and output the rectified voltage signal to the overvoltageprotection branch, and the overvoltage protection branch determineswhether to turn off the electrical path of the LED module according tothe inputted voltage signal and the preset voltage threshold, wherein:

during an ascending stage of an absolute value of voltage, thealternating current in the alternating current module passes through thefifth diode D5 and the first capacitor C1 to form a loop so as to chargethe first capacitor C1; meanwhile, the alternating current passesthrough the fourth capacitor C4 and the third diode D3 to form a loop soas to charge the fourth capacitor C4; meanwhile, the second capacitorC2, the third capacitor C3, the first diode D1 and the LED module form aloop so as to supply power to the LED module, i.e., electric chargesstored in the second capacitor C2 and the third capacitor C3 aredischarged to the LED module through the first diode D1, so as toprovide the working voltage for the LED module.

In the embodiments of the present disclosure, during the chargingprocess in the ascending stage of the alternating current voltage, inthe circuit structure, the first capacitor C1 and the fourth capacitorC4 are connected in parallel, the second capacitor C2 and the thirdcapacitor C3 are connected with the alternating current module inseries, such that the absolute value of voltage of the alternatingcurrent is increased when switching the alternating current, so as toenable the LED module to be turned on in advance.

In the embodiments of the present disclosure, through the alternativecharging and discharging of the first capacitor C1, the second capacitorC2, the third capacitor C3 and the fourth capacitor C4 during thepositive and negative half cycles of the alternating current, thevoltage value outputted to the LED module becomes relatively stable, andthe flickering frequency of the LED module when emitting light isreduced; meanwhile, the turn-on time of the LED module within thepositive and negative half cycles of the alternating current isincreased, the fluctuation of light emitted by the LED module isreduced, and the power factor of the circuit is improved. Further, thecircuit in the embodiments of the present disclosure has a simplestructure, has a high efficiency of power supply, and is very suitablefor the illumination device in which the LED module is directly drivenby the alternating current.

In actual applications, in order to ensure that a difference between theoutput currents of the alternating current within the positive andnegative half cycles is small, in FIGS. 2 and 3, the equivalentresistances of respective branches should be the same or similar, i.e.,diode parameters in respective branches should be the same or similar,and respective capacitors should also have the same or similarcapacitances. For example, the diode parameters in the positive halfcycle rectifying branch should be the same as or similar with the diodeparameters in the negative half cycle rectifying branch; and thecapacitance in the positive half cycle feeding branch should be the sameas or similar with the capacitance in the negative half cycle feedingbranch.

In the embodiments of the present disclosure, selecting the capacitorshaving the same or similar parameters brings benefit to improve theelectrical balance, and also brings benefit to balance the load, reducethe flickering and improve efficiency of power supply. In theembodiments of the present disclosure, the charging and dischargingcharacteristic of the capacitor is mainly utilized, thereby thecapacitance (capacitivity) parameters are the most important parameters.By selecting the capacitors having the same or similar capacitances, thecharging and discharging characteristics can substantially reach thesame or similar level.

Preferably, in order to further improve the stability of the voltagesignal outputted to the LED module, the alternating current rectifyingcircuit for driving an LED module in the embodiments of the presentdisclosure further includes a current regulative diode (CRD).

FIG. 4 is a schematic diagram illustrating another detailed structure ofan alternating current rectifying circuit for driving an LED moduleaccording to an embodiment of the present disclosure. Referring to FIG.4, different from FIG. 3, a current regulative diode (CRD) is furtherincluded, wherein a positive terminal of the CRD is connected with thesource of the field effect transistor M1, and a negative terminal of theCRD is connected with the positive terminal of the third diode D3. Inthis way, by adding one current regulative diode for limiting current inthe DC loop, the luminous efficiency of the LED module can be greatlyimproved.

In FIG. 3, although the embodiments of the present disclosure can solvethe problem of fluctuation of the light outputted from the LED module toa certain extent, the degree of filling the trough of the alternatingcurrent is low. The light outputted from the LED module at the trough ofthe alternating current is only 30%˜40% of the light outputted at thepeak.

Thereby, a preferable solution of the present disclosure is provided asshown in FIG. 5.

FIG. 5 is a schematic diagram illustrating further another detailedstructure of an alternating current rectifying circuit for driving anLED module according to an embodiment of the present disclosure.Referring to FIG. 5, different from FIG. 4, on the basic circuit of thepresent disclosure, an electrolytic capacitor C5 is added as a filtercapacitor, wherein a positive terminal of the electrolytic capacitor C5is connected with the input terminal of the LED module, and a negativeterminal of the electrolytic capacitor C5 is connected with the outputterminal of the LED module. Thus, due to filtering function of theelectrolytic capacitor C5, the current wave flowing into the LED moduleis smoother. Although some power factors are sacrificed, the lightoutputted from the LED module at the trough of the alternating currentcan reach more than 80% of the light outputted at the peak, thus thereis mostly no difference of the sense.

FIG. 6 is a flow chart of an alternating current rectifying method fordriving an LED module according to an embodiment of the presentdisclosure. Referring to FIG. 6, the alternating current rectifyingcircuit drives a light emitting diode LED module. The current rectifyingcircuit includes: an alternating current module, a positive half cyclerectifying branch, a positive half cycle feeding branch, a negative halfcycle rectifying branch, a negative half cycle feeding branch, and anovervoltage protection branch. The method includes the following steps.

In step 601, when the alternating current module is in a positive halfcycle, the positive half cycle rectifying branch rectifies analternating current outputted from the alternating current module, andoutputs the rectified voltage signal to the overvoltage protectionbranch and an external LED module.

In this step, the positive half cycle rectifying branch includes a firstrectifying tube, a second rectifying tube and a sixth rectifying tube,wherein:

a positive terminal of the second rectifying tube is connected with oneend of the alternating current module, and a negative terminal of thesecond rectifying tube is connected with a positive terminal of thefirst rectifying tube;

a negative terminal of the first rectifying tube is connected with aninput terminal of the external LED module;

a positive terminal of the sixth rectifying tube is connected with anoutput terminal of the external LED module, and a negative terminal ofthe sixth rectifying tube is connected with the other end of thealternating current module.

The overvoltage protection branch includes a first resistor, a secondresistor, a third resistor, a fourth resistor, a fifth resistor, a firstZener diode, a second Zener diode, a NPN transistor and a field effecttransistor, wherein:

one end of the first resistor is connected with one end of the fourthresistor and an input terminal of the LED module, and the other end ofthe first resistor is connected with one end of the second resistor, anegative terminal of the first Zener diode and one end of the thirdresistor;

the other end of the third resistor is connected with a base of the NPNtransistor;

the other end of the fourth resistor is connected with a collector ofthe NPN transistor, one end of the fifth resistor and a negativeterminal of the second Zener diode;

the other end of the fifth resistor is connected with a gate of thefield effect transistor;

a drain of the field effect transistor is connected with the outputterminal of the LED module;

a source of the field effect transistor is connected with the other endof the second resistor, a positive terminal of the first Zener diode, anemitter of the NPN transistor, a positive terminal of the second Zenerdiode and a positive terminal of the third rectifying tubes.

In step 602, the negative half cycle feeding branch performs chargingaccording to the alternating current outputted from the alternatingcurrent module, and the positive half cycle feeding branch performsdischarging and outputs the discharged voltage signal to the overvoltageprotection branch and the external LED module.

In this step, the negative half cycle feeding branch includes a secondcapacitor and a third capacitor, wherein:

one end of the second capacitor is connected with one end of thealternating current module, and the other end of the second capacitor isconnected with the output terminal of the external LED module; and

one end of the third capacitor is connected with the positive terminalof the first rectifying tube, and the other end of the third capacitoris connected with the other end of the alternating current module.

The positive half cycle feeding branch includes a first capacitor and afourth capacitor, wherein:

one end of the first capacitor is connected with the positive terminalof the fourth rectifying tube, and the other end of the first capacitoris connected with one end of the alternating current module; and

one end of the fourth capacitor is connected with the other end of thealternating current module, and the other end of the fourth capacitor isconnected with the output terminal of the external LED module.

In step 603, the overvoltage protection branch turns off an electricalpath of the external LED module when the inputted voltage signal ishigher than a preset voltage threshold.

In step 604, when the alternating current module is in the negative halfcycle, the negative half cycle rectifying branch rectifies thealternating current outputted from the alternating current module, andoutputs the rectified voltage signal to the overvoltage protectionbranch circuit and the external LED module.

In this step, the negative half cycle rectifying branch includes a thirdrectifying tube, a fourth rectifying tube and a fifth rectifying tube,wherein:

a negative terminal of the third rectifying tube is connected with oneend of the alternating current module, and a positive terminal of thethird rectifying tube is connected with the output terminal of theexternal LED module;

a positive terminal of the fifth rectifying tube is connected with theother end of the alternating current module, and a negative terminal ofthe fifth rectifying tube is connected with a positive terminal of thefourth rectifying tube;

a negative terminal of the fourth rectifying tube is connected with theinput terminal of the external LED module.

In step 605, the negative half cycle feeding branch performsdischarging, and outputs the discharged voltage signal to theovervoltage protection branch and the external LED module, and thepositive half cycle feeding branch performs charging according to thealternating current outputted from the alternating current module.

In step 606, the overvoltage protection branch turns off an electricalpath of the external LED module when the inputted voltage signal ishigher than the preset voltage threshold.

Thus, in the embodiments of the present disclosure, during the positivehalf cycle of the alternating current, current passes through the secondrectifying tube, the first rectifying tube, the LED module and the sixthrectifying tube to form a loop so as to supply power to the LED module,and output the rectified voltage signal to the overvoltage protectionbranch, and the overvoltage protection branch determines whether to turnoff the electrical path of the LED module according to the inputtedvoltage signal and the preset voltage threshold, wherein:

during an ascending stage of the alternating current voltage, thealternating current passes through the second rectifying tube and thethird capacitor to form a loop so as to charge the third capacitor;meanwhile, the alternating current passes through the second capacitorand the sixth rectifying tube to form a loop so as to charge the secondcapacitor; meanwhile, the fourth capacitor, the first capacitor, thefourth rectifying tube and the LED module form a loop so as to supplypower to the LED module;

during the negative half cycle of the alternating current, currentpasses through the fifth diode, the fourth rectifying tube, the LEDmodule and the third rectifying tube to form a loop so as to supplypower to the LED module, and output the rectified voltage signal to theovervoltage protection branch, and the overvoltage protection branchdetermines whether to turn off the electrical path of the LED moduleaccording to the inputted voltage signal and the preset voltagethreshold, wherein:

during an ascending stage of an absolute value of voltage, thealternating current in the alternating current module passes through thefifth rectifying tube and the first capacitor to form a loop so as tocharge the first capacitor; meanwhile, the alternating current passesthrough the fourth capacitor and the third rectifying tube to form aloop so as to charge the fourth capacitor; meanwhile, the secondcapacitor, the third capacitor, the first rectifying tube and the LEDmodule form a loop so as to supply power to the LED module.

Apparently, the person skilled in the art can make various modificationsand changes to the present disclosure without departing from the spiritand scope thereof. Thus, if the modifications and changes to the presentdisclosure are within the scope of the claims of the present disclosureand its equivalent technique, the present disclosure intends to containsuch modifications and changes.

1. An alternating current rectifying circuit for driving a load module,characterized in that, the alternating current rectifying circuitcomprises: an alternating current module, a positive half cyclerectifying branch, a positive half cycle feeding branch, a negative halfcycle rectifying branch, a negative half cycle feeding branch, and anovervoltage protection branch, wherein: the positive half cyclerectifying branch is configured to, when the alternating current moduleis in a positive half cycle, rectify an alternating current outputtedfrom the alternating current module, and output a rectified voltagesignal to the overvoltage protection branch and an external load module;the positive half cycle feeding branch is configured to perform chargingaccording to the alternating current outputted from the alternatingcurrent module when the alternating current module is in a negative halfcycle; and perform discharging and output a discharged voltage signal tothe overvoltage protection branch and the external load module when thealternating current module is in the positive half cycle; the negativehalf cycle rectifying branch is configured to, when the alternatingcurrent module is in the negative half cycle, rectify the alternatingcurrent outputted from the alternating current module, and output arectified voltage signal to the overvoltage protection branch and theexternal load module; the negative half cycle feeding branch isconfigured to perform charging according to the alternating currentoutputted from the alternating current module when the alternatingcurrent module is in the positive half cycle; and perform dischargingand output a discharged voltage signal to the overvoltage protectionbranch and the external load module when the alternating current moduleis in the negative half cycle; and the overvoltage protection branch isconfigured to turn off an electrical path of the external load modulewhen the inputted voltage signal is higher than a preset voltagethreshold.
 2. The alternating current rectifying circuit according toclaim 1, wherein the positive half cycle rectifying branch comprises afirst rectifying tube, a second rectifying tube and a sixth rectifyingtube, wherein: a positive terminal of the second rectifying tube isconnected with one end of the alternating current module, and a negativeterminal of the second rectifying tube is connected with a positiveterminal of the first rectifying tube; a negative terminal of the firstrectifying tube is connected with an input terminal of the external loadmodule; and a positive terminal of the sixth rectifying tube isconnected with an output terminal of the external load module, and anegative terminal of the sixth rectifying tube is connected with theother end of the alternating current module.
 3. The alternating currentrectifying circuit according to claim 2, wherein the negative half cyclerectifying branch comprises a third rectifying tube, a fourth rectifyingtube and a fifth rectifying tube, wherein: a negative terminal of thethird rectifying tube is connected with the one end of the alternatingcurrent module, and a positive terminal of the third rectifying tube isconnected with the output terminal of the external load module; apositive terminal of the fifth rectifying tube is connected with theother end of the alternating current module, and a negative terminal ofthe fifth rectifying tube is connected with a positive terminal of thefourth rectifying tube; and a negative terminal of the fourth rectifyingtube is connected with the input terminal of the external load module.4. The alternating current rectifying circuit according to claim 3,wherein the positive half cycle feeding branch comprises a firstcapacitor and a fourth capacitor, wherein: one end of the firstcapacitor is connected with the positive terminal of the fourthrectifying tube, and the other end of the first capacitor is connectedwith the one end of the alternating current module; and one end of thefourth capacitor is connected with the other end of the alternatingcurrent module, and the other end of the fourth capacitor is connectedwith the output terminal of the external load module.
 5. The alternatingcurrent rectifying circuit according to claim 4, wherein the negativehalf cycle feeding branch comprises a second capacitor and a thirdcapacitor, wherein: one end of the second capacitor is connected withthe one end of the alternating current module, and the other end of thesecond capacitor is connected with the output terminal of the externalload module; and one end of the third capacitor is connected with thepositive terminal of the first rectifying tube, and the other end of thethird capacitor is connected with the other end of the alternatingcurrent module.
 6. The alternating current rectifying circuit accordingto claim 3, wherein the overvoltage protection branch comprises a firstresistor, a second resistor, a third resistor, a fourth resistor, afifth resistor, a first Zener diode, a second Zener diode, a NPNtransistor and a field effect transistor, wherein: one end of the firstresistor is connected with one end of the fourth resistor and the inputterminal of the LED module, and the other end of the first resistor isconnected with one end of the second resistor, a negative terminal ofthe first Zener diode and one end of the third resistor; the other endof the third resistor is connected with a base of the NPN transistor;the other end of the fourth resistor is connected with a collector ofthe NPN transistor, one end of the fifth resistor and a negativeterminal of the second Zener diode; the other end of the fifth resistoris connected with a gate of the field effect transistor; a drain of thefield effect transistor is connected with the output terminal of theload module; and a source of the field effect transistor is connectedwith the other end of the second resistor, a positive terminal of thefirst Zener diode, an emitter of the NPN transistor, a positive terminalof the second Zener diode and a positive terminal of the thirdrectifying tube.
 7. The alternating current rectifying circuit accordingto claim 6, wherein the rectifying tubes are diodes, transistors orsilicon controlled rectifiers.
 8. The alternating current rectifyingcircuit according to claim 6, wherein the first capacitor, the secondcapacitor, the third capacitor and the fourth capacitor are non-polarcapacitors.
 9. The alternating current rectifying circuit according toclaim 8, wherein the first capacitor, the second capacitor, the thirdcapacitor and the fourth capacitor have the same capacitance value. 10.The alternating current rectifying circuit according to claim 9, whereinduring the positive half cycle of the alternating current, the currentpasses through the second diode, the first diode, the load module andthe sixth diode to form a loop so as to supply power to the load module,and output the rectified voltage signal to the overvoltage protectionbranch, and the overvoltage protection branch determines whether to turnoff the electrical path of the load module according to the inputtedvoltage signal and the preset voltage threshold, wherein: during anascending stage of voltage of the alternating current, the alternatingcurrent passes through the second diode and the third capacitor to forma loop so as to charge the third capacitor; meanwhile, the alternatingcurrent passes through the second capacitor and the sixth diode to forma loop so as to charge the second capacitor; meanwhile, the fourthcapacitor, the first capacitor, the fourth diode and the load moduleform a loop so as to supply power to the load module; during thenegative half cycle of the alternating current, the current passesthrough the fifth diode, the fourth diode, the load module and the thirddiode to form a loop so as to supply power to the load module, andoutput the rectified voltage signal to the overvoltage protectionbranch, and the overvoltage protection branch determines whether to turnoff the electrical path of the load module according to the inputtedvoltage signal and the preset voltage threshold, wherein: during anascending stage of an absolute value of voltage, the alternating currentin the alternating current module passes through the fifth diode and thefirst capacitor to form a loop so as to charge the first capacitor;meanwhile, the alternating current passes through the fourth capacitorand the third diode to form a loop so as to charge the fourth capacitor;meanwhile, the second capacitor, the third capacitor, the first diodeand the load module form a loop so as to supply power to the loadmodule.
 11. The alternating current rectifying circuit according toclaim 10, further comprising: a current regulative diode with a positiveterminal connected with the source of the field effect transistor and anegative terminal connected with the positive terminal of the thirddiode.
 12. The alternating current rectifying circuit according to claim11, further comprising: an electrolytic capacitor with a positiveterminal connected with the input terminal of the load module and anegative terminal connected with the output terminal of the load module.13. An alternating current rectifying method for driving a load module,wherein the load module is driven by an alternating current rectifyingcircuit and the alternating current rectifying circuit comprises: analternating current module, a positive half cycle rectifying branch, apositive half cycle feeding branch, a negative half cycle rectifyingbranch, a negative half cycle feeding branch, and an overvoltageprotection branch, the method comprising the steps of: when thealternating current module is in a positive half cycle, rectifying bythe positive half cycle rectifying branch rectifies an alternatingcurrent outputted from the alternating current module, and outputting arectified voltage signal to the overvoltage protection branch and anexternal load module; performing by the negative half cycle feedingbranch charging according to the alternating current outputted from thealternating current module, and performing by the positive half cyclefeeding branch discharging and outputting a discharged voltage signal tothe overvoltage protection branch and the external load module; andturning off by the overvoltage protection branch an electrical path ofthe external load module when the inputted voltage signal is higher thana preset voltage threshold; and when the alternating current module isin the negative half cycle, rectifying by the negative half cyclerectifying branch the alternating current outputted from the alternatingcurrent module, and outputting a rectified voltage signal to theovervoltage protection branch circuit and the external load module;performing by the negative half cycle feeding branch discharging, andoutputting a discharged voltage signal to the overvoltage protectionbranch and the external load module, and performing by the positive halfcycle feeding branch charging according to the alternating currentoutputted from the alternating current module; and turning off by theovervoltage protection branch the electrical path of the external loadmodule when the inputted voltage signal is higher than the presetvoltage threshold.
 14. The alternating current rectifying methodaccording to claim 13, wherein the positive half cycle rectifying branchcomprises a first rectifying tube, a second rectifying tube and a sixthrectifying tube, wherein: a positive terminal of the second rectifyingtube is connected with one end of the alternating current module, and anegative terminal of the second rectifying tube is connected with apositive terminal of the first rectifying tube; a negative terminal ofthe first rectifying tube is connected with an input terminal of theexternal load module; and a positive terminal of the sixth rectifyingtube is connected with an output terminal of the external load module,and a negative terminal of the sixth rectifying tube is connected withthe other end of the alternating current module.
 15. The alternatingcurrent rectifying method according to claim 14, wherein the negativehalf cycle rectifying branch comprises a third rectifying tube, a fourthrectifying tube and a fifth rectifying tube, wherein: a negativeterminal of the third rectifying tube is connected with the one end ofthe alternating current module, and a positive terminal of the thirdrectifying tube is connected with the output terminal of the externalload module; a positive terminal of the fifth rectifying tube isconnected with the other end of the alternating current module, and anegative terminal of the fifth rectifying tube is connected with apositive terminal of the fourth rectifying tube; and a negative terminalof the fourth rectifying tube is connected with the input terminal ofthe external load module.
 16. The alternating current rectifying methodaccording to claim 15, wherein the positive half cycle feeding branchcomprises a first capacitor and a fourth capacitor, wherein: one end ofthe first capacitor is connected with the positive terminal of thefourth rectifying tube, and the other end of the first capacitor isconnected with the one end of the alternating current module; and oneend of the fourth capacitor is connected with the other end of thealternating current module, and the other end of the fourth capacitor isconnected with the output terminal of the external load module.
 17. Thealternating current rectifying method according to claim 16, wherein thenegative half cycle feeding branch comprises a second capacitor and athird capacitor, wherein: one end of the second capacitor is connectedwith the one end of the alternating current module, and the other end ofthe second capacitor is connected with the output terminal of theexternal load module; and one end of the third capacitor is connectedwith the positive terminal of the first rectifying tube, and the otherend of the third capacitor is connected with the other end of thealternating current module.
 18. The alternating current rectifyingmethod according to claim 15, wherein the overvoltage protection branchcomprises a first resistor, a second resistor, a third resistor, afourth resistor, a fifth resistor, a first Zener diode, a second Zenerdiode, a NPN transistor and a field effect transistor, wherein: one endof the first resistor is connected with one end of the fourth resistorand the input terminal of the load module, and the other end of thefirst resistor is connected with one end of the second resistor, anegative terminal of the first Zener diode and one end of the thirdresistor; the other end of the third resistor is connected with a baseof the NPN transistor; the other end of the fourth resistor is connectedwith a collector of the NPN transistor, one end of the fifth resistorand a negative terminal of the second Zener diode; the other end of thefifth resistor is connected with a gate of the field effect transistor;a drain of the field effect transistor is connected with the outputterminal of the load module; and a source of the field effect transistoris connected with the other end of the second resistor, a positiveterminal of the first Zener diode, an emitter of the NPN transistor, apositive terminal of the second Zener diode and a positive terminal ofthe third rectifying tube.
 19. The alternating current rectifying methodaccording to claim 18, wherein the rectifying tubes are diodes, duringthe positive half cycle of the alternating current, the current passesthrough the second diode, the first diode, the load module and the sixthdiode to form a loop so as to supply power to the load module, andoutput the rectified voltage signal to the overvoltage protectionbranch, and the overvoltage protection branch determines whether to turnoff the electrical path of the load module according to the inputtedvoltage signal and the preset voltage threshold, wherein: during anascending stage of voltage of the alternating current, the alternatingcurrent passes through the second diode and the third capacitor to forma loop so as to charge the third capacitor; meanwhile, the alternatingcurrent passes through the second capacitor and the sixth diode to forma loop so as to charge the second capacitor; meanwhile, the fourthcapacitor, the first capacitor, the fourth diode and the load moduleform a loop so as to supply power to the load module; during thenegative half cycle of the alternating current, the current passesthrough the fifth diode, the fourth diode, the load module and the thirddiode to form a loop so as to supply power to the load module, andoutput the rectified voltage signal to the overvoltage protectionbranch, and the overvoltage protection branch determines whether to turnoff the electrical path of the load module according to the inputtedvoltage signal and the preset voltage threshold, wherein: during anascending stage of an absolute value of voltage, the alternating currentin the alternating current module passes through the fifth diode and thefirst capacitor to form a loop so as to charge the first capacitor;meanwhile, the alternating current passes through the fourth capacitorand the third diode to form a loop so as to charge the fourth capacitor;meanwhile, the second capacitor, the third capacitor, the first diodeand the load module form a loop so as to supply power to the loadmodule.
 20. The alternating current rectifying method according to claim18, wherein the present voltage threshold is set by setting theresistances of the first resistor and the second resistor.